Breeding bird communities of a managed forest landscape in coastal North Carolina
Recent concern for the status of North American bird populations has resulted in an escalation of monitoring and management efforts. Much of this effort has been focused on declining forest-dwelling species that migrate between breeding areas in North America and wintering areas in Latin America and the Caribbean. Fragmentation of temperate forests has been shown to negatively affect many of these species by exposing them to higher rates of predation and brood parasitism, resulting in lower productivity and survivorship. Weyerhaeuser Company is the largest private landowner in North Carolina. Because of the extent and geographic location of current landholdings, Weyerhaeuser's forest tracts offer the opportunity to manage populations of declining bird species at a landscape scale. This project was initiated to examine the underlying relationship between the vegetative structure and the breeding bird community within managed pine plantations. Breeding bird communities were sampled within a network of forest stands located in the coastal plain of North Carolina. All stands were located on Weyerhaeuser land and were chosen to represent points along the forest management cycle and to reflect natural variation in understory vegetation. A total of 24,490 bird observations were made of 70 species during the two year study period. Both species richness and bird abundance were positively related to stand age. Early successional stands (ages 1 through 11) and forest stands (all stands after first thin) had distinctly different vegetation structures and bird communities. Early successional bird communities were dominated by species generally associated with grasslands and shrublands. Species turnover rates were higher in early successional stands compared to forest stands, reflecting differences in the rates of vegetation change. Forest bird communities were dominated by habitat generalists and species typically associated with closed canopy forests. In general, forest birds showed little discrimination between stand categories after the first commercial thinning. The large canopy openings created during commercial thinning allowed for understory regeneration and had a positive influence on both species richness and overall bird density. These openings appear to have extended the habitat use of some early successional species and provided habitat elements required by some forest bird species. Thinning events had a particularly positive influence on the use of stands by Brown-headed Nuthatches, a southeastern pinewoods endemic. A few species detected during surveys are of special interest because of their relative rarity or are of high conservation priority within the region. Worm-eating Warblers were detected in densities that regionally have only been reported from the Great Dismal Swamp. Black-throated Green and Swainson's Warblers showed similar patterns. Black-and-white Warblers were detected in low densities and may also only occur at a few sites within the immediate region.